The present invention relates to a method of making belting and, more particularly, to a method of making belting useful in round, hay balers.
In agricultural applications, belts are used for a wide variety of purposes, from transmitting power to conveying produce. For example, hay balers use belts to form hay into a bale. In a typical round, hay baler, eight to fifteen rollers support four to eight individual belts, each of which is typically about 40 feet long.
Rigorous demands are placed on belts used in round, hay balers. The belts serve not only as conveying media, but also as size restrictors and compaction devices. This rigorous service is in sharp contrast to the service performed by the more prevalent conveyor belt. The conveyor belt is generally limited to service as a carrying and actuating medium.
The most common type of belt used in hay balers today is a three-ply belt, such as the belt disclosed in U.S. Pat. No. 4,371,580 (Morrison et al.). The belt typically is comprised of three fabric plies coupled by two inner rubber skims that form the belt core and two outer rubber skims that protect the core surfaces. A brief description of the three-ply belt's conventional manufacturing technique is in order. First, large sheets of fabric for the center ply and the outer plies are primed with a bonding chemical such as resorcinol formaldehyde latex (RFL). Uncured inner rubber skims and outer rubber covers are then alternated with the fabric sheets. The plied sheets are then vulcanized to form the appropriate bonds, and the belts are cut to the appropriate lengths and widths from the large three-ply sheet.
The most common method of belt production from large processed sheets such as the three-ply sheet mentioned above is the `cut-edge` belt method. The belts are produced by slitting the large sheets of processed material into individual belts of the proper width. This exposes the edges of the fabric plies that form the core of the belt. The belt ends of the individual belts are then fastened together to produce continuous, cut-edge, loop belts. While these loop belts have been well received, they are not without problems.
A first such problem lies in the fact that the longitudinal edges of the belts produced by the cut-edge method tend to delaminate when the belts are subjected to the loads and stresses of a hay-baling operation. This delamination along the longitudinal edges contributes to deterioration of the means used to fasten the ends of the belt together, especially along the longitudinal edges.
A second problem with cut-edge belting is caused by uneven infeeding of the crop into the baler. The crop pushes material into the side of the belt which tends to force the belt off a straight path of travel. This causes the edges of the belt to wear excessively, and the wear becomes progressively worse with use.
Moreover, the edges of cut-edge belts and other types of belts tend to curl up against the mechanical guides on the rollers. This curling induces an even greater amount of stress and flexion at the edges of the belt and, thus, contributes to accelerated fatigue at the edges of the belt.
A common problem with all current hay baler belts results from the heavy loads they are subjected to as they travel around the rollers when baling. The belt edges tend to stretch more than the center of the belt. This is due, at least partially, to an unbalance of load or force dissipation as the load shifts off the belt's center. This unbalanced load results from the gaps between the belts in the hay baler. When the belts are acting as compressors on the hay bale, the hay tends to bulge out between the gaps resulting in greater stress on the edges of the belt and thus greater elongation.
Another common problem with available belting is belt rollover. Current belts deform along the leading edge of a sideward moving belt. This deformation tends to brake the belt along the leading edge which causes the leading edge to roll under and the rest of the belt to roll over this leading edge. This rollover results in detrimental elongation of the belt edge which interferes with proper baler operation and contributes to deterioration of the belt.
The current methods of attaching belt ends to form continuous loop belts also create problems within the belts. The ends of cut-edge and other belts are typically joined by one of two methods. In a first method, mechanical fasteners are used to join the ends of each belt to form an endless belt. A commonly used mechanical fastener known as a "clipper lace" splice is described in U.S. Pat. No. 4,371,580 (Morrison et al.), incorporated herein by reference. A clipper lace splice includes a plurality of metal eyelets that are connected to each end of the belt. When the eyelets on each end of the belt are aligned with one another, a rod or other suitable retaining material is passed through the eyelets. The ends of the rod are suitably formed to prevent removal of the rod so that the splice remains intact.
The mechanical fasteners tend to deteriorate belts in several ways. First, the mechanical fasteners tend to wear and fail at a faster rate along the longitudinal edges of the belts because of the force exerted on the belt edge by the hay bales. If a mechanical fastener on a hay baler fails, the belt must be replaced before the hay baler can continue operating.
Second, because of the excessive wear on the outer-edge fasteners, they are damaged and effectively lost. This damage puts the central fasteners under greater tension which, in turn, can cause damage to these fasteners.
U.S. Pat. No. 4,279,676 (Morrison et al.), incorporated herein by reference, discloses a second method for joining the ends of cut-edge and other belts. This method solves some of the retention problems associated with mechanical fasteners by splicing the ends of the belt to form an endless loop. While the endless splice has proven successful in improving the reliability of the fastened belt, the increased cost of the endless splice has slowed its acceptance in the industry.
While belts have been improved over the years to minimize or overcome various problems, no known belt satisfactorily minimizes or overcomes the problems mentioned above. Two-ply belts, where the plies are made of a polyamide fabric, such as Nylon (a trademark of DuPont), exhibit excellent flexing characteristics, but also possess a relatively high modulus. In an effort to solve the elongation problem, a two-ply belt was developed where the plies were made of a rayon material. Rayon has a lower modulus than a polyamide fabric and, hence, does not stretch as much as a polyamide belt under the same load. However, the rayon belt proved to be unacceptable, since rayon is particularly susceptible to environmental deterioration caused by moisture. In another attempt to solve the elongation problem, a two-ply belt was developed where the plies were made of a polyester material. This belt proved ineffective since the polyester plies tended to crack when flexed, and the cracking was most pronounced in the area of the mechanical fastener.
A subsequently developed three-ply belt exhibited improved flexing and stretching characteristics as compared with the above-mentioned two-ply belts. The center ply was a polyester fabric, and each outer ply was a polyamide fabric. Interposed between the center ply and each outer ply was a rubber skim. These materials were bonded together, and a rubber cover was bonded to each outer ply to provide abrasion protection for the belt and to give the machinery on which the belt was used a surface to engage when the belt was in operation.
One suggested solution for several of the problems associated with cut-edge belts and mechanical fasteners has been to put a rubber cap on the exposed edges of the belts. This solution was described in U.S. Pat. Nos. 4,900,609 (Arnold) and 4,371,580 (Morrison et al.). This rubber cap has consisted of the same material used on the outer surfaces of the belt. The cap has helped slow down wear on the inner, fabric plies that were exposed in cut-edge belts. It has also provided shock resistance for the mechanical fasteners such as when the belt comes into contact with the mechanical guides.